The majority of highly effective sunscreens are oily or oil-soluble. These sunscreens are necessary for UV blocking, but have an unpleasant heavy, oily skin feel and present formulation difficulties such as sunscreen solubility and compatibility with other components. To counter the heavy, oily skin feel associated with sunscreen compositions, such products are commonly formulated as emulsions. The majority of such emulsions are oil-in-water emulsions wherein the aqueous phase (which in most cases is predominantly water) is thickened with polymeric thickeners. One problem with oil-in-water emulsions is that, being water-based, they too easily rinse or rub off of the skin, e.g., after perspiring, swimming, or washing hands. Considerably fewer sunscreen compositions in the form of an inverse emulsion (water-in-oil) exist. Inverse emulsions have a tendency to feel greasy and heavy. There is a desire to provide a sunscreen composition comprising a water-in-oil emulsion which has a pleasant skin feel and which does not rinse or rub off of the skin too easily. To accomplish this desire, silicone oil may be incorporated into the composition as the primary oil-phase component.
With the incorporation of silicone oil into a sunscreen composition, however, other issues become critical, such as sunscreen solubility. Poor sunscreen solubility leads to the sunscreen precipitating out of the oil phase at certain concentrations or temperatures, resulting in crystals that the user can see and feel, as well as compositions with reduced or limited UV protection benefits. Generally, it is easier to solubilize liquid sunscreens in silicone oil than it is to solubilize solid sunscreens in silicone oil. For broad spectrum UV protection, it is typically necessary to use a combination of UV-A blocking sunscreens and UV-B blocking sunscreens. While effective UV-B blocking sunscreens are available in both liquid and solid form, almost all of the most effective UV-A blocking sunscreens currently approved for use are only available in solid form. A polar-oil solvent may be used to help solubilize solid UV-A blocking sunscreens, but as more solvent is added to a composition, the more greasy, heavy, and unpleasant the composition feels. There is a need to improve the solubility in silicone oil of solid UV-A blocking sunscreens without the addition of more solvent, so that even at high concentrations or temperatures the solid sunscreens do not separate out of the oil phase. Further, there is a need to provide a sunscreen composition with a pleasant skin feel and sufficient UV blocking.